Could The Delayed Periods Be Due To Pregnancy?

Hello me and my husband are trying to have our second child. I sign up for an ovulation tracking system on line. I followed the information. I was told that on 03/29/2010 a pregnancy test would work. I have take two one on the 27th then on the 29th,it was negative,but my period is two days late. I'm scared if i test again it would be negative.